The Magpul PRS is a drop-in, precision-adjustable butt stock for rifles with A1 or A2 fixed stocks. Designed to offer the fine-tuned, customized feel of a precision target stock, the PRS is adjustable for both cheek riser height and length of pull without sacrificing the durability necessary to withstand the operational environment. The PRS is a direct replacement for an A1 or A2 fixed stock. Fitting to a Carbine will require a Rifle Receiver Extension tube, Rifle Buffer and Spring.